IISc-Bengaluru, Canada astronomers detect radio signal from distant galaxy, all details here

The team also observed that the atomic hydrogen mass of this particular galaxy is almost twice as high as its stellar mass

IISc-Bengaluru, Canada astronomers detect radio signal from distant galaxy, all details here
Illustration showing detection of the lensed 21 cm atomic hydrogen emission signal from a distant galaxy. (Photo Credits: Swadha Pardesi/ IISc)

Astronomers from McGill University in Canada as well as the Indian Institute of Science (IISc) which is in Bengaluru have detected a radio signal which is originating from atomic hydrogen in an extremely distant galaxy.  

This has been possible due to the data which has been used from the Giant Metrewave Radio telescope (GMRT) in Pune. The following findings have been published in ‘Monthly Notices of the Royal Astronomical Society’.  

In its report, IISc has said, “The astronomical distance over which such a signal has been picked up is the largest so far by a large margin. This is also the first confirmed detection of strong lensing of 21 cm emission from a galaxy.”

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How was the data found?

To begin with, atomic hydrogen is the basic fuel which is required for the formation of a star in a galaxy. When hot ionised gas from the surrounding medium of a galaxy falls onto the galaxy, the gas cools down and forms atomic hydrogen, leading to the formation of molecular hydrogen. It eventually leads to the formation of stars, as the study explains.

Atomic hydrogen emits radio waves of 21 cm wavelength, which can be detected using low-frequency radio telescopes like the GMRT. Thus, 21 cm emission is a direct tracer of the atomic gas content in both nearby and distant galaxies, said the report produced by IISc on its website.

However, the signal which has been detected is very faint and it is almost impossible to detect the emission from a distant galaxy using current telescopes due to their limited sensitivity.

To which, the report read, “ Until now, the most distant galaxy detected using 21 cm emission was at redshift z=0.376, which corresponds to a look-back time – the time elapsed between detecting the signal and its original emission – of 4.1 billion years (Redshift represents the change in wavelength of the signal depending on the object’s location and movement; a greater value of z indicates a farther object).”

With the help of GMRT data, Arnab Chakraborty, who is a post-doctoral researcher at the Department of Physics and Trottier Space Institute of McGill University, and Nirupam Roy, Associate Professor, the Department of Physics, IISc, has detected a radio signal from atomic hydrogen in a distant galaxy at redshift z=1.29.

Nirupam Roy in his statement in the report has stated, that this detection was possible due to a phenomenon called gravitational lensing, in which the light emitted by the source is bent due to the presence of another massive body, such as an early type elliptical galaxy, between the target galaxy and the observer, effectively resulting in the “magnification” of the signal. “In this specific case, the magnification of the signal was about a factor of 30, allowing us to see through the high redshift universe.  

Other than this the team also observed that the atomic hydrogen mass of this particular galaxy is almost twice as high as its stellar mass.  These results demonstrated the practicality of observing atomic gas from other galaxies at cosmological distances in similar lensed systems with a modest amount of observing time.

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First published on: 19-01-2023 at 15:47 IST
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